1. Field of the Invention
This invention relates generally to steering wheels for automotive vehicles and particularly to such a steering wheel which is provided with shock-absorbing means.
2. Description of Related Art
Various safety devices have been proposed for protecting a vehicle driver against the influence of a shock generated as in a vehicle collision accident. A typical example of such a device is an air bag housed in the steering wheel pad. This shock-absorbing device however has a drawback in that it is very costly and requires a relatively large space for installation. With a view to coping with the problems, it has been proposed in lieu of air bags to use shock-absorbing means comprised of a urethane resin or a steel skeleton material.
However, it has been ascertained as depicted in FIG. 11 of the accompanying drawings that although the urethane shock-absorbing material receives a relatively low initial load immediately upon a vehicle collision, it is susceptible to an increase in the buckling load with an increase in the stroke of an ensuing crush of the material, departing away from the desired shock-absorption characteristics where the buckling load should be held as much constant as possible.
With the steel skeleton material, this exhibits a sharp rise in the initial load immediately upon collision and then temporarily sustains a relatively low buckling load profile commensurate with an increase in the crush stroke but the buckling load soon resumes a sharp upward curve as illustrated in FIG. 12.
Thus, neither of the above two alternatives has proven to be successful in shock-energy absorbing performance called for in the event of a car accident such as a head-on crush. A further disadvantage is that a collapsible device formed from either of the above resinous and steel materials requires increased thickness in a direction along which its crash stroke extends, contributing to a large dimension of the steering wheel pad.